Decurling mechanism

Abstract

A decurling mechanism for performing a decurling process of correcting the curl of paper includes: a first roller; a second roller disposed travelably around the first roller; and a roller position changing mechanism for changing the second roller to a plurality of positions set on a traveling path of the second roller. The plurality of positions include a decurling position in which the decurling process to the paper is enabled and the paper is conveyed while being pinched between the first and second rollers, a conveyance position in which the decurling process to the paper is disabled and the paper is conveyed while being pinched between the first and second rollers and a pinch release position in which the paper is released from the pinch between the first and second rollers.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims priority under 35 USC 119 to Japanese Patent Application No. 2008-018320 filed on Jan. 29, 2008, the entire contents of which are incorporated herein by reference.BACKGROUND[0002]The techniques disclosed in this specification relate to decurling mechanisms for performing a decurling process of correcting a curl of paper.[0003]In conventional printers used such as for photographic printing systems, their printer body includes a paper containing part for containing a long web of rolled paper (a long rolled paper web). The paper web contained in the paper containing part is fed to a printing part and printed therein by a print head, such as an inkjet print head. The printed paper web is cut in a given length and then conveyed to an output point at which, for example, a paper output tray is disposed.[0004]Since the paper web is rolled around a core, it has a curled shape due to a core set. Therefore, if cut pieces of th...

AI Technical Summary

Benefits of technology

[0009]The present invention has been made in view of the foregoing points and, therefore, an object thereof is to provide a decurling mechanism that subjects curled paper to a decurling process with a simple structure but does not subject paper with no curl to a decurling process and that can prevent an indentation of a decurling roller from being left on the paper upon stop of paper conveyance during the decurling process.

[0012]Specifically, when, for example, a piece of rolled paper is conveyed, the decurling mechanism moves the second roller to the decurling position and subjects the paper to the decurling process, whereby the curl of the paper can be corrected. On the other hand, when, for example, a paper sheet is conveyed, the decurling mechanism moves the second roller to the conveyance position and can convey the paper sheet without subjecting it to the decurling process. Thus, the paper sheet originally having no curl can be prevented from being subjected to the decurling process and thereby being curled. This provides a decurling mechanism that can appropriately handle a piece of rolled paper and a paper sheet.

[0013]Furthermore, when the paper conveyance is stopped, the pressing of the second roller against the paper can be released by moving the second roller in decurling process from the decurling position to the pinch release position. For example, when in an inkjet printer the paper conveyance is temporarily stopped owing to intermittent paper conveyance in order to form an image on the paper, the movement of the second roller from the decurling position to the pinch release position can eliminate an inconvenience that an indentation of the second roller is left on the paper and the printing quality is thereby deteriorated.

[0015]With the above configuration, a greater clearance is created between the first and second rollers than the case where both the rollers are vertically juxtaposed with respect to the direction of paper conveyance. Thus, the pinching force of both the rollers against the paper can be reduced to reduce the load applied to the paper. Specifically, the paper is conveyed in a slightly sagging state. Therefore, even if the pinching force is reduced, the restoring force of the paper towards stretching straight and the frictional force between the paper and both the rollers provide smooth conveyance of the paper using the resilience of the paper.

[0017]With the above configuration, an appropriate decurling force to the shape of a curl of paper can be applied to the paper by adjusting the strength of the decurling force. Specifically, part of a paper web in the vicinity of the core around which the paper web is rolled has a small radius of curvature and is therefore strongly curled, while part of the paper web in the vicinity of the outer periphery thereof has a large radius of curvature and is therefore weakly curled. To cope with this, the strength of the decurling force is adjusted according to the amount of use of the rolled paper web. Thus, the curl of the paper can be corrected with an optimum decurling force.

[0019]With the above configuration, the dryer dries ink adhering to the paper in the printing part. When dried by the dryer, the paper is heated by dry air and is therefore easily deformable. Since, in addition, the first and second rollers are disposed downstream of the dryer in the direction of paper conveyance, the paper can be subjected to the decurling process while held easily deformable. This provides a high decurling effect.

Problems solved by technology

If the above decurling mechanism is simply added to the printer such as for the photographic printing system, paper sheets originally having no curl are also subjected to a decurling process, which is unfavorable because the paper sheets are unnecessarily curled oppositely to the curl of a rolled paper web.

This complicates the printer structure.

If an indentation of the decurling roller is left on the paper upon stop of paper conveyance, this invites a problem that the print quality is deteriorated.

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